1. Field of the Invention
This invention generally relates to electric lamps and has particular reference to an improved incandescent reflector lamp that is suitable for use as the light source in warning-signal apparatus of the type employed at railroad crossings and the like.
2. Description of the Prior Art
As is well known, visual warning of an approaching train at railway crossings is provided by a flashing red light that is part of the signalling apparatus located at each crossing. In order to ensure that pedestrian and vehicular traffic see the warning light on bright sunny days when the ambient light level is very high, the warning light system must be such that it concentrates the light rays into a very narrow and intense beam of light that is directed toward the traffic. In addition, suitable means must be provided to permit the engineer of an approaching train to quickly and reliably determine whether the warning-signal lamp is actually operating properly.
In the railway-crossing signalling apparatus now in use, the aforesaid requirements are met by mounting a miniature incandescent light bulb in focussed relationship with a separate reflector within the housing of the signalling apparatus so that the light rays pass through a red-colored lens located on the front of the housing. Aligned openings in the sides of the lamp-housing and reflector component permit the train engineer to view the interior of the housing and thus visually verify that the light bulb and warning signal are operating normally as the train approaches the crossing.
Electric lamps that contain a light source which is disposed within a light-reflecting housing or enclosure are generally well-known in the art and have been used for many years, in the form of automobile sealed-beam headlamps for example. A headlamp having an outer parabolic reflector and a lens cover that are joined together and form a housing which contains a lamp bulb and an inner auxiliary reflector that has a pair of window-apertures which permit some of the light to strike the outer reflector and then pass through the lens in order to provide a beam pattern which makes efficient use of the total light flux emitted by the lamp bulb is disclosed in U.S. Pat. No. 3,184,592 granted May 18, 1965 to P. Cibie.
An electric lamp assembly that is designed for use in a light projector and consists of an outer bulb of light-transmitting material (such as "strengthened" glass) which encloses a halogen-type electric lamp bulb and is provided with a plurality of heat-radiating holes or "pores" is disclosed in Japanese Pat. Publication No. 49-28380 published Mar. 11, 1974 and granted to C. Kotake.